Tetramethylsilane standard nuclear magnetic resonance

The nuclear magnetic resonance spectrum of sodium valproate as shown in Figure 3 was obtained on a Varian Associates T-60 NMR Spectrometer in deuterium oxide containing tetramethylsilane as the internal standard. The spectral peak assignments (2) are presented in Table I. 

Since the product slowly darkens on exposure to air, it should be stored under nitrogen in a refrigerator. The compound solidifies on cooling m.p. 16.0-16.5°. Nuclear magnetic resonance spectrum (neat, tetramethylsilane internal standard) singlets at d 7.00 (aromatic protons), 3.93 (CH2), and 2.24 p.p.m. (NH). 

Infrared (IR) spectra were measured on a Beckmann Microlab 600 model spectrophotometer. Nuclear magnetic resonance (NMR) spectra were measured on a Varian EM360 spectrometer, with 19F-spectra collected using trifluoroacetic acid as a standard, or with H-spectra collected using tetramethylsilane as a standard. 

All NMR spectra were recorded on a Varian A-60 spectrometer at room temperature by Nuclear Magnetic Resonance Specialties, Inc., New Kensington, Pa. Benzene soluble fractions were recorded in deuterated chloroform solution (CDCls) while dimethyl sulfoxide-dc (DMSO-dr.) was the solvent employed for other fractions. (Deuterated chloroform with enrichment of 99.8% was purchased from Bio-Rad Laboratories and dimethyl sulfoxide-dr, with enrichment of 99.6% from Merck, Sharp, and Dohme of Canada.) The internal standard used with the CDCla solutions was tetramethvlsilane and hexamethyl-disiloxane (chemical shift 7 c.p.s.) with DMSO-d . Prior to preparation for NMR recording, the samples were thoroughly dried in a vacuum at 110°C. The NMR tubes were sealed to minimize the absorption of atmospheric moisture. The chemical shifts given in c.p.s. are referred to tetramethylsilane. 

H NMR spectrum The proton nuclear magnetic resonance (1H NMR) spectrum of omeprazole were obtained using a Bruker Instrument operating at 300,400, or 500 MHz. Standard Bruker Software was used to execute the recording of DEPT, COSY, and HETCOR spectra. The sample was dissolved DMSO-d6 and all resonance bands were referenced to tetramethylsilane (TMS) as internal standard. The H NMR spectra of omeprazole are shown in Figs. 4.9-4.12 and the COSY H NMR is... 

Nuclear magnetic resonance (NMR) spectrometry [4] Both the 1H NMR and 13C NMR spectra of zaleplon have been obtained in DMSO- as a solvent and using tetramethylsilane as the internal standard (IS). The assignments for both the 1H and 13C NMR spectra make use of the following numbering scheme ... 

The following tables give the region of the expected nuclear magnetic resonance absorptions of major chemical families. These absorptions are reported in the dimensionless units of parts per million (ppm) vs. the standard compound tetramethylsilane (TMS), which is recorded as 0.0 ppm ... 

Nuclear Magnetic Resonance Spectroscopy. Nmr is a most valuable technique for structure determination in thiophene chemistry, especially because spectral interpretation is much easier in the thiophene series compared to benzene derivatives. Chemical shifts in proton nmr are well documented for thiophene (CDC13), 6 = H2 7.12, H3 7.34, H4 7.34, and H5 7.12 ppm. Coupling constants occur in well-defined ranges J2 3 = 4.9-5.8 J3 4 = 3.45-4.35 J2 4 = 1.25-1.7 and J2 5 = 3.2-3.65 Hz. The technique can be used quantitatively by comparison with standard spectra of materials of known purity. 13C-nmr spectroscopy of thiophene and thiophene derivatives is also a valuable technique that shows well-defined patterns of spectra. 13C chemical shifts for thiophene, from tetramethylsilane (TMS), are C2 127.6, C3 125.9, C4 125.9, and C5 127.6 ppm. 

Fig. 3. —Nuclear Magnetic Resonance Spectrum of Methyl 5-Acetamido-5-deoxy-2,3,4-tri-O-methyl-a-D-xylopyranoside (210). [Taken at 100 MHz in tetiachloroethane at 35°, lower curve at 110°, upper curve tetramethylsilane as internal standard.]...

Instruments Batch experiments for obtaining CL profiles were performed using a Microtec NITI-ON Lumicounter 2500 (Chiba, Japan). Proton nuclear magnetic resonance ( H-NMR) spectra were obtained on a JEOL JNM-EX270 spectrometer (Tokyo, Japan) with tetramethylsilane as an internal standard. Mass spectra (FAB-MS) were measured on a JEOL JMS-LXIOOO (Tokyo, Japan) with w-nitrobenzyl alcohol as a matrix. 

The nuclear magnetic resonance (NMR) spectra were recorded on a Varian A-60 spectrometer, using deuterated dimethyl sulfoxide (DMSO) as solvent and tetramethylsilane as internal standard. IR spectra were obtained on a Perkin-Elmer 237B IR spectrophotometer. 

Nuclear magnetic resonance analysis with double and triple resonance was used to elucidate the structure as 3, 4 -dideoxykanamycin B 2"-adenylate. The spectrum of the inactivated 3, 4 -dideoxykanamycin B in deuterium oxide at pH 8.0, with tetramethylsilane as the external reference standard (8 =0), showed signals at 8 8.63 and 8.85 attributable to the adenine-ring protons, and at 8 6.53, 5.28, 4.98, 4.83 and 4.6 (H-2) the latter were assigned to the D-ribose-ring protons by successive doubleresonance experiments, and by comparison with disodium 5 -adenylate in deuterium oxide. Therefore, these observations confirmed the presence of one molecular proportion of 5 -adenylic acid in the molecule. Irradiation at 8 5.45 (7 3.6, H-1") caused the complex signal at 8 4.3 (H-2")... 

A) Schematic diagram of a simple nuclear magnetic resonance (NMR) spectrometer. The sample is placed in solution in a long, thin tube and spins in a probe sitting in a magnetic and surrounded by radio-frequency (RF) coils B) proton NMR spectrum of ethanol (QH O) with tetramethylsilane (TMS) added as internal standard. On the 8-scale of chemical shifts,... 

Melting points were measured in open capillary tubes in a Scientific Glass Co. melting point apparatus. Melting points and boiling points are uncorrected. The nuclear magnetic resonance spectral data presented were obtained with a Varian model T-60 spectrophotometer using dimethylsulfoxide or tetramethylsilane as an internal standard. A Perkin-Elmer Model 137 Sodium Chloride spectrophotometer was used to record infrared spectra. 

Determination of PHA polymer composition by nuclear magnetic resonance (NMR). Twenty mg of each polymer was dissolved in 1 ml of CDCI3 and subjected to both H and C NMR analysis. H NMR spectra were recorded using a JEOL a-400 spectrometer with a 5.0 ps pulse width (45 pulse angle), 3-s pulse repetition, 7500-Hz spectra width, and 16K data points. For C NMR analysis, ta were collected using a JEOL ECP-500 spectrometer with a 7.0-ps pulse width (45° pulse angle), 5-s pulse repetition, 25000-Hz spectra width, and 64K data points. Tetramethylsilane (Me4Si) was used as an internal chemical shift standard. 

Proton nuclear magnetic resonance spectra are recorded on a Bruker WB UM 360 or a Bruker SP200 spectrometer with tetramethylsilane as internal standard the signals are described as s, singulet d, doublet t, triplet q, quartet, m, multiplet br, broad Ar-H, aromatique. 

The structure of SPEKs was usually determined by nuclear magnetic resonance (NMR) analysis. For each analysis, 3 wt.% polymer solution was prepared in deuterated dimethyl sulfoxide (DMSO-tfg) for HNMR and 15 wt.% for CNMR. The chemical shift of tetramethylsilane was used as the internal standard reference. The typical HNMR spectrum and its chemical shift assignment for SPEEK obtained by the postsulfonation method are also shown in Figure 5.14. 

Chemical shift relates the Larmor frequency of a nuclear spin to its chemical environment l 3. The Larmor frequency is the precession frequency v0 of a nuclear spin in a static magnetic field (Fig. 1.1). This frequency is proportional to the flux density Bo of the magnetic field (v0 B0 = const.) 3. It is convenient to reference the chemical shift to a standard such as tetramethylsilane [TMS, (C//j)4Si] rather than to the proton ft. Thus, a frequency difference (Hz) is measured for a proton or a carbon-13 nucleus of a sample from the H or 13C resonance of TMS. This value is divided by the absolute value of the Larmor frequency of the standard (e.g. 400 MHz for the protons and 100 MHz for the carbon-13 nuclei of TMS when using a 400 MHz spectrometer), which itself is proportional to the strength B0 of the magnetic field. The chemical shift is therefore given in parts per million (ppm, 5 scale, SH for protons, 5C for carbon-13 nuclei), because a frequency difference in Hz is divided by a frequency in MHz, these values being in a proportion of 1 106. 

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